Kleiner Perkins Caufield & Byers has agreed to invest in the fast-growing ephemeral message service Snapchat Inc. at a valuation of close to $10 billion, people with knowledge of the matter said.Snapchat, which has talked to several potential investors in recent months, is in the process of raising a large investment round that would make it one of the world’s most valuable private tech startups despite virtually no revenue. Kleiner, one of Silicon Valley’s best-known venture-capital firms, committed to invest up to $20 million in May, one of the knowledgeable people said. At least one strategic investor has also committed to invest in the round, which isn’t yet closed, two of the people said. DST Global, the Russian investment firm led by Yuri Milner, also invested in Snapchat earlier this year at a valuation of $7 billion, according to two people familiar with the matter.